1. Field of the Invention
The present invention relates to an external wall element for buildings.
2. Description of Related Art
From German Laid Open 27 52 178, external wall elements are known that have two parallel panes between which solar cells are arranged for generating energy. However, such external wall elements are not translucent. External wall elements are known from German Laid Open 31 25 622 that are provided with a fluorescent pane arranged between two parallel panes. For the purpose of generating energy, photoelectric cells are provided at the rim of the fluorescent pane. This external wall element allows the passage of light however, the energy efficiency of the photoelectric cells is low and what is more, the incident radiation energy passing into a building cannot be regulated. German Laid Open 30 05 914 describes a solar collector having a pane with a plurality of holographic elements arranged side by side. Arrays of solar cells are arranged at a distance behind the holographic elements, which are sensitive to different spectral ranges. The holographic elements focus the radiation of the different wavelengths onto the respective associated solar cells. This solar collector is not designed as an external wall element for buildings and it is not able to transmit light or heat radiation, so that it cannot be used for illumination purposes.
It is an object of the present invention to provide an external wall element for buildings which permits an effective exploitation of the solar radiation for illuminating and heating the building or for energy generation purposes.